1. Field of the Invention
This invention relates to a method and apparatus for measuring the composition of a zinc phosphate compound and, more particularly, to a method and apparatus for measuring the concentration of hopeite and phosphophyllite on an article of manufacture.
2. Discussion
Zinc phosphate compounds are used to coat steel parts of automobiles and other types of machinery thereby imparting a high degree of corrosion resistance to the same. The degree of corrosion resistance so imparted is usually dependent upon the concentration of hopeite and phosphophyllite contained within the zinc phosphate compound. Therefore precise measurements of these contained concentrations must continuously be made in order to ensure product quality. Such measurements are usually made during an assembly process of the component.
Current approaches used to determine this hopeite and phosphophyllite concentration include the SEM, ESCA, and Auger methodologies as well as x-ray diffractometry and similar techniques used to study the microscopic structure of surfaces. These techniques, while effective, involve some sort of special preparation of the vehicle or sample under study (e.g., the vehicle must be placed within a vacuum). Thusly, these techniques are not suitable for on-line or non-contact monitoring and therefore production time and resources are wasted during this testing time resulting in inefficient assembly processes.